Interview Q&A

Short answer: Yes. Variables inside the outer function cannot be accessed directly, only via inner functions.

Example code

See createCounter() above.

Real-world example (ShopNest)

In ShopNest’s cart UI, a click handler closes over productId. Use let in loops so each button keeps the correct id.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Install React-Bootstrap (npm install react-bootstrap bootstrap). Import components: import { Button } from 'react-bootstrap'; <Button variant="primary">Click</Button>

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Both execute dynamic code, but: eval() executes in the current scope (less safe). Function() executes in a new scope (safer). Example: eval("var a = 5"); const b = new Function("return 5;"); ⚠ Both are discouraged due to security and performance issues. Bootstrap Interview Questions

Example code

Both execute dynamic code, but: eval() executes in the current scope (less safe). Function() executes in a new scope (safer). Example: eval("var a = 5");
const b = new Function("return 5;"); ⚠ Both are discouraged due to security and performance issues. Bootstrap Interview Questions

Real-world example (ShopNest)

In ShopNest’s cart UI, a click handler closes over productId. Use let in loops so each button keeps the correct id.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Use try...catch inside async functions or .catch() for Promises. Example: async function loadData() { try { const res = await fetch('/data'); return await res.json(); } catch (err) { console.error("Error:", err); } Follow me on LinkedIn: } Advanced

Example code

Use try...catch inside async functions or .catch() for Promises. Example: async function loadData() { try { const res = await fetch('/data');
return await res.json(); } catch (err) { console.error("Error:", err); } Follow me on LinkedIn: } Advanced

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Using try...catch...finally or Promise .catch(). Example: try { throw new Error("Something went wrong!"); } catch (err) { console.error(err.message); } finally { console.log("Cleanup code"); } Intermediate

Example code

Using try...catch...finally or Promise .catch(). Example: try { throw new Error("Something went wrong!"); } catch (err) { console.error(err.message); } finally { console.log("Cleanup code"); }
Intermediate

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Lexical scoping means that the scope of a variable is determined by its position in the source code. Inner functions have access to variables declared in their outer scope.

Example code

function outer() { let name = "Sandeep"; function inner() { console.log(name); // accesses outer variable } inner(); } outer(); // Sandeep

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Reboot is a modernized CSS reset that standardizes browser styles for consistent rendering. Follow me on LinkedIn:

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: An object is a collection of key-value pairs used to store related data and functions. Example: let person = { name: "Sandeep", age: 30 };

Example code

An object is a collection of key-value pairs used to store related data and functions. Example: let person = { name: "Sandeep", age: 30 };

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Reusable SCSS functions that generate CSS dynamically. Example: @include border-radius(10px);

Example code

Reusable SCSS functions that generate CSS dynamically. Example: @include border-radius(10px);

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Using object literal: {} Using new Object() constructor Example: let car = { brand: "Tesla", model: "Model 3" }; let car2 = new Object(); car2.brand = "BMW";

Example code

Using object literal: {} Using new Object() constructor Example: let car = { brand: "Tesla", model: "Model 3" };
let car2 = new Object();
car2.brand = "BMW";

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Wrap the table in .table-responsive: <div class="table-responsive"> <table class="table">...</table> </div>

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Functions defined inside objects are called methods.

Example code

let person = { name: "Sandeep", greet() { console.log(`Hello, ${this.name}`); } }; person.greet(); // Hello, Sandeep

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Import only needed components via SCSS. Use tools like PurgeCSS to remove unused classes. Use custom builds from Bootstrap’s build system.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: this refers to the context in which a function is called.

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: rrow: () => console.log(this.name), // undefined in global regular() { console.log(this.name); } // Sandeep }; obj.regular(); obj.arrow(); rrow: () => console.log(this.name), // undefined in global regular() { console.log(this.name); } // Sandeep }; obj.regular(); obj.arrow(); rrow: () => console.log(this.name), // undefined in global regular() {… console.log(this.name); } // Sandeep }; obj.regular(); obj.arrow();…

Explain a bit more

rrow: () => console.log(this.name), // undefined in global regular() { console.log(this.name); } // Sandeep }; obj.regular(); obj.arrow();

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Load Bootstrap first, then your custom CSS to override styles. Use namespacing or BEM methodology to prevent conflicts. Combine selectively via SCSS imports. Follow me on LinkedIn:

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Global function: this = window (browser) Object method: this = the object Arrow function: this = lexical context (inherits from parent scope)

Example code

const obj = { name: "Sandeep", arrow: () => console.log(this.name), // undefined in global regular() { console.log(this.name); } // Sandeep }; obj.regular(); obj.arrow();

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Extract values from objects into variables. Example: const person = { name: "Sandeep", age: 30 }; const { name, age } = person; console.log(name, age); // Sandeep 30

Example code

Extract values from objects into variables. Example: const person = { name: "Sandeep", age: 30 };
const { name, age } = person; console.log(name, age); // Sandeep 30

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Arrays are ordered collections of values. Example: let numbers = [1, 2, 3, 4];

Example code

Arrays are ordered collections of values. Example: let numbers = [1, 2, 3, 4];

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: for loop for...of forEach Example: numbers.forEach(n => console.log(n));

Example code

for loop for...of forEach Example: numbers.forEach(n => console.log(n));

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Extract elements from arrays into variables. Example: let [first, second] = [10, 20]; console.log(first, second); // 10 20

Example code

Extract elements from arrays into variables. Example: let [first, second] = [10, 20]; console.log(first, second); // 10 20

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Allows expanding arrays or objects. Example: let arr1 = [1, 2]; let arr2 = [...arr1, 3, 4]; // [1,2,3,4] let obj1 = { a: 1 }; let obj2 = { ...obj1, b: 2 }; // { a:1, b:2 }

Example code

Allows expanding arrays or objects. Example: let arr1 = [1, 2];
let arr2 = [...arr1, 3, 4]; // [1,2,3,4]
let obj1 = { a: 1 };
let obj2 = { ...obj1, b: 2 }; // { a:1, b:2 }

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: JavaScript objects inherit properties and methods from other objects through prototypes. This allows reuse of methods and shared behavior. Example: const parent = { greet() { console.log("Hello"); } };

Example code

const child = Object.create(parent); child.greet(); // Hello

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The prototype chain is the chain of objects that JavaScript follows to look up properties or methods. If a property isn’t found on the object itself, JS checks the object's prototype, and continues up the chain.

Example code

console.log(child.toString()); // from Object.prototype

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Objects inherit from other objects via Object.create(), constructor functions, or classes (ES6). Methods can be shared via prototypes. Example using constructor: function Person(name) { this.name = name; } Person.prototype.greet = function() { console.log(`Hello ${this.name}`); }; const p = new Person("Sandeep"); p.greet(); // Hello Sandeep

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.